.3(x-5)(6x+12)=0

Solution for .3(x-5)(6x+12)=0 equation:

.3(x-5)(6x+12)=0

We multiply parentheses ..

.3(+6x^2+12x-30x-60)=0

We multiply parentheses

1.8x^2+3.6x-9x-18=0

We add all the numbers together, and all the variables

1.8x^2-5.4x-18=0

a = 1.8; b = -5.4; c = -18;
Δ = b2-4ac
Δ = -5.42-4·1.8·(-18)
Δ = 158.76
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5.4)-\sqrt{158.76}}{2*1.8}=\frac{5.4-\sqrt{158.76}}{3.6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5.4)+\sqrt{158.76}}{2*1.8}=\frac{5.4+\sqrt{158.76}}{3.6}
$